the second variant doesn't create a lexical.

Neither does the first!

our only gives lexical visibility; not a true lexical variable.

Ie. With my, it creates an entirely new variable at each level of scope:

my $a = 123; 
{ 
    my $a; 
    print $a; ## produces "Use of uninitialized value $a in print ... 
+" because the above new $a is entirely new; thus uninitialised.
}

print $a;; ## prints: 123
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However, our only gives lexically scoped access to a single variable:

our $a = 123; 
{ 
    our $a; ## produces ""our" variable $a redeclared at ..." referenc
+es the same variable as the first our $a
    print $a; ## prints 123 ## New scope, same variable, existing valu
+e.
} 
print $a;; ##  prints 123
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